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If the first essential cold period appears already in November or early December, the water 
gets indeed rapidly cooled, but it is often not enough for significant ice formation. If this 
period is interrupted by a long period with positive air temperatures, or there are several cold 
periods in the winter, but of small strength, then the sum of coldness is relatively large, the ice 
production keeps at the level of mild ice winters. 
Differences of the behaviour of average ice parameters in mild, moderate and strong ice 
winters are shown in Figures 2.8. -2.10. 
Pomeranian Bay first ice Pomeranian Bay last ice 
Szczecin Lagoon first ice —■—Szczecin Lagoon last ice 
Mild Moderate Strong 
Figure 2.8. Average dates of first and last ice in Szczecin Lagoon and Pomeranian Bay 
in different ice winter classes 
Pomeranian Bay days —±— Pomeranian Bay duration 
Szczecin Lagoon days —■— Szczecin Lagoon duration 
Mild Moderate Strong 
Figure 2.9. Average number of days with ice and duration of the ice season in Szczecin 
Lagoon and Pomeranian Bay in different ice winter classes